We implement a novel and accurate discrete fracture (DF) method to simulate fracture-matrix flow in geologically representative networks. The aim of the work is to study the interplay of viscous, capillarity and buoyancy-controlled displacement. We eliminate the smearing effect created by combining fracture and matrix control volumes in current finite element approaches that average fluid properties (saturation, density, etc) between the two media and have unrealistic control volumes around DFs. As a result, a very fine mesh is necessary to represent the system accurately, drastically increasing the number of nodes. Applications: This work is applicable to modeling and simulating fluid flow in heavily fractured reservoirs with complex geometry. Discussion and Results: In this paper, we give DFs a separate 1D or 2D control volume, depending on element, distinct from the matrix control volume. Both communicate through a Darcy law equation that depends on fracture aperture and matrix-fracture transmissibility, while maintaining the same inter-phase pressure between the two media. This approach facilitates the extensive use of DFs, thus allowing a new type of dual porosity, dual permeability mesh where the 2D triangular elements (DF) surround matrix blocks (made out of four tetrahedrons) instead of using the overlapped idea of matrix and fractures made out of the same element type, while having fewer nodes. Fracture-matrix displacement, using fracture networks based on outcrops, is studied to show the advantages of the new approach compared to the conventional method. This allows us to study displacement processes during water flooding in mixed-wet fractured reservoirs. Significance: Develop a new type of dual porosity dual permeability mesh with the geometrical advantage of finite elements.


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